A gravitational method of beneficiation of coal to be used for power generation is known (see, for example, Mitchell, D. R. Coal Preparation, New York: American Institute of Mining, 1950; Tsiperovich M. V. Coal beneficiation in heavy media, Moscow: Metallurgizdat, 1953).
According to this method, rock mass produced in the coalface is delivered by underground mine transport to the shaft bottom and then lifted to the surface using mine pulling unit, crushed and submerged into a liquid medium with the density intermediate between those of the fossil fuel and the waste rock, which represents powdery magnetite suspension in water. As a result, the solid fuel, as the lightest component of this system, floats in this heavy medium, whereas the waste rock sinks.
After the extraction of beneficiation products out of the heavy medium and regeneration of magnetite suspension residues carried out to the surface, the enriched solid fuel is dried and delivered by railway or other transport to a thermoelectric power station for combustion, whereas humid beneficiation rejects are either stored on the ground surface in the form of waste piles or, in order to prevent land alienation and ground surface subsidence, lowered back into the mine, transported to the backfilling place and located wet in the mined-out space.
The above method is characterized by obviously unpractical power consumption for drawing waste rock from the coal mine to the surface as a part of rock mass and for bringing back waste beneficiation products to the place of their placement in the mined-out space, as well as by an intense environment pollution with coal dust during numerous transfers and transportations of the enriched solid fuel by railway to a thermoelectric power station owing to a strong blowing-out of dusty fractions of this dry free-flowing material by the wind.
The closest to the method of the present invention is a method of solid fuel beneficiation consisting in the stratification of minerals composing crushed rock mass in a true aqueous medium representing a solution of some soluble mineral salt in water, whose density is intermediate between those of the target component and waste rock, with subsequent extraction of beneficiation products, their washing with water from concomitant residues, evaporation of the obtained flows and return of the regenerated heavy water-salt medium to the starting point of the technological process (see, for instance, ‘Washing coal: Patent 1724 Great Britain, Cl. 82’).
However, the described method is characterized by a significant irreversible water consumption caused by the outlet of final tailings wetted with water out of the beneficiation system, as well as by high energy consumption for the evaporation of flows formed in the process of washing beneficiation products with water for the regeneration of the heavy water-salt medium.
Besides, the impossibility (for aero-logical reasons) of underground placement of the evaporation facility in the immediate vicinity of the placement of final tailings of beneficiation in the worked-out area, leads to the necessity of the delivery of the entire rock mass volume to the ground surface and, consequently, to the over-expenditure of power resources for the transportation of such an essential fraction of this ballast component.
Meanwhile, the delivery of dry enriched fuel from the ground-based beneficiation plant to the electric power station by railway, as already emphasized, is accompanied by easy blowing of its dusty fractions by the wind, which leads not only to significant loss of the delivered cargo, but also to an intense environment pollution with fuel dust, especially in places of transfer of this dusty material.